Measuring mass-loss rates from Galactic satellites

We present the results of a study that uses numerical simulations to interp ret observations of tidally disturbed satellites around the Milky Way. When analysing the simulations from the viewpoint of an observer, we find a bre ak in the slope of the star count and velocity dispersion profiles in our m odels at the location where unbound stars dominate. We conclude that 'extra tidal' stars and enhanced velocity dispersions observed in the outskirts of Galactic satellites are caused by contamination by stellar debris from the tidal interaction with the Milky Way. However, a significant bound populat ion can exist beyond the break radius and we argue that it should not be id entified with the tidal radius of the satellite. We also develop and test a method for determining the mass-loss rate from a Galactic satellite using its extra-tidal population. We apply this method to observations of globular clusters and dwarf spheroidal satellites of the Milky Way, and conclude that a significant fraction of each of these satel lite systems is likely to be destroyed within the next Hubble time. Finally, we demonstrate that this mass-loss estimate allows us to place som e limits on the initial mass function (IMF) of stars in a cluster from the radial dependence of its present-day mass function (PDMF).